Questions about 2011 v70 d3

[Wower]

Hello,

I got few questions. First is it safe to use 205/55/R16 wheels on 2011 v70 d3? Long story short I bought brand new tires for another car. That car got written off at the start of December. Now I got this volvo and would like to use those tires if I can, as it would be cheaper than buying new ones.

Second question: Few days ago my car started doing one weird thing. After I start driving it I get unusually high revs. Like 1.5k While driving slowly and 2.5k when I accelerate, also it switches gears at hlmuch higher rpm. It does settle down after I drive for 1-2km. And then I get the usual 800rpm and it runs smoothly from there. Funny thing this only happens once when I start the car for the first time, for the next starts nothing like this happens. Is this normal behavior or is something malfunctioning?

Thanks